Is a battery worth it? The honest arithmetic

The case in one sentence

A battery is worth it when the gap between what you pay for grid power and what you're paid for exports is large enough, and your evening usage is high enough, that storing your own generation beats selling it - by enough to recover the battery's cost within a period you're comfortable with.

Start with the gap

Look at your bill. Find your usage rate (what you pay per kilowatt-hour) and your feed-in tariff (what you're paid per kilowatt-hour exported). In NSW these typically sit around 30-40 cents and 4-8 cents respectively - meaning every kilowatt-hour you store and use instead of exporting is worth roughly the difference.

A 13.5 kWh battery cycling most of its capacity daily might therefore avoid $3 to $4 of grid purchases a day where it would have earned well under a dollar exporting. Over a year that's meaningful - but it only works if you actually have that much surplus generation and that much evening load to soak it up.

The two conditions that must both hold

You need surplus solar. A battery charges from what your panels produce beyond what the house is using at the time. A modest array on a house with heavy daytime usage may generate very little surplus - nothing to store.

You need evening load. The stored energy has to be consumed, ideally daily. A household that's empty in the evening and uses most of its power at midday doesn't need storage - their solar is already being self-consumed at full value.

This is why we ask when you use power, not just how much. A daytime-heavy household and an evening-heavy household with identical bills need completely different systems.

What the rebate changed

The federal battery rebate - the Cheaper Home Batteries Program - materially shortened battery payback by discounting the upfront cost. Batteries between 5 kWh and 100 kWh on approved product lists qualify, with incentives typically applying to the first 50 kWh. It applies whether you're adding storage to existing solar or installing a new system together.

Two things worth knowing. The rebate is applied to your price upfront by the installer, not claimed back by you later. And it steps down at intervals - the value available today is higher than the value available later, which is a real consideration if you were already going to install this year.

It does not, however, turn a bad battery case into a good one. If you don't have surplus solar and evening load, a discounted battery is still money spent for little return.

The non-financial reasons

Some people buy batteries for reasons the arithmetic doesn't capture: blackout protection for essential circuits, insulation from future price rises, or simply wanting to use their own generation rather than sell it cheaply. Those are legitimate reasons and we won't argue you out of them - but we'll be clear about which part of your decision is financial and which part isn't.

How to actually decide

Get your daily usage and its rough time distribution from your bill. Get your usage rate and feed-in tariff from the same bill. Model the surplus your proposed array would produce, and how much of it your evening load could absorb. Compare the annual value of that stored energy against the rebated battery cost.

That's the calculation our design tool runs, and it's the calculation an engineer should show you the working for. If someone quotes you a battery without asking when you use power, they haven't done it.